Oxide superconductor and method of producing same

Abstract

A high critical temperature and high critical current density superconductor containing a matrix phase of a metal oxide expressed by the formula RE 1 Ba 2 Cu 3 O p wherein RE 1 stands for La, Nd, Sm, Eu or Gd and p is a number of 6.8-7.2, a first dispersed phase of a metal oxide expressed by the formula RE 2 1+d Ba 2-d Cu 3 O q wherein RE 2 stands for La, Nd, Sm, Eu or Gd, d is a number of 0<d<0.5 and q is a number of 6.0-7.2 and a second dispersed phase of a metal oxide expressed by the formula RE 3 4-2x Ba 2+2x Cu 2-x O 10-y wherein RE stands for La or Nd, x is a number of 0<x .English Pound.0.25 and y is a number of 0<y<0.5. The first and second phases are dispersed in the matrix. The above superconductor may be prepared by cooling a partial melt having a temperature of 1,000°-1,300° C. and containing a major molar amount of RE 1 Ba 2 Cu 3 O p and a minor molar amount of RE 3 4-2x Ba 2+2x Cu 2-x O 10-y at a cooling rate of 10° C./hour or less.

What is claimed is: 
     
       1. A process for the production of a superconductor, comprising heating a mixture to a temperature of 1,000°-1,300° C. said mixture containing a major molar amount of RE 1  Ba 2  Cu 3  O p  wherein RE 1  stands for at least one element selected from the group consisting of La, Nd, Sm, Eu and Gd and p is a number between 6.8 and 7.2 and a minor molar amount of RE 3   4-2x  Ba 2+2x  Cu 2-x  O 10-y  wherein RE 3  stands for at least one element selected from the group consisting of La and Nd, x is a number greater than 0 but not greater than 0.25 and y is a number not smaller than 0 but smaller than 0.5 and subsequently cooling said mixture at a cooling rate of 10° C./hour or less, thereby to form a superconducting phase. 
     
     
       2. A process as claimed in claim 1, wherein said cooling is performed under a partial pressure of oxygen of at least 0.1 atm. 
     
     
       3. A process as claimed in claim 1, wherein said cooling is performed at a cooling rate of 5° C./hour or less. 
     
     
       4. A process as claimed in claim 1, wherein said cooling is performed under a partial pressure of oxygen of not lower than 0.00001 atm but lower than 0.1 atm and wherein x is a number greater than 0.1 but not greater than 0.25. 
     
     
       5. A process as claimed in claim 1, wherein said melt contains powder of a component selected from the group consisting of platinum and CeO 2  in an amout of not more than 1% based on the total weight of said RE 1  Ba 2  Cu 3  O p  and said RE 3   4-2x  Ba 2+2x  Cu 2-x  O 10-y .